1. Field of the Invention
The present invention relates to an image processing in an image forming apparatus.
2. Description of the Related Art
Conventionally, as a example of when a copying and the like of both sides of a document is realized in a digital copier, there is a method of using a document feeder that scans the front side of the document, and then reverses the document, and scans the back side of the document. The productivity of this method is low because the reading of the front side of the document and the back side thereof cannot be performed concurrently. Recently, to achieve higher productivity, a digital copier has appeared that reads the front of the document and the back side thereof concurrently with two reading units. Furthermore, to meet demands for full-color printing and high image quality, a digital copier capable of reading and writing data at a high resolution has appeared.
However, if the demands for full color printing and high image quality and the demand for high productivity are met in one device, an image quality difference between the image data depending on a difference in the reading characteristics of the two reading units can become remarkable. To take care of this, it is necessary to reduce the image quality difference between the image data by the image processing.
Japanese Patent Application Laid-open No. 2006-135631 discloses an image forming apparatus in which the image quality difference between the image data depending on the difference in the reading characteristics of the reading units is reduced by image processing based on the reading characteristics of the reading units that are the same as each other or different from each other. This conventional image forming apparatus includes a single image processing unit that performs predetermined image processing on each of image data read by a first image reading unit and image data read by a second image reading unit, and a correction processing unit that performs processing to correct a difference between the reading characteristics of the first image reading unit and the second image reading unit on either one of the image data read by the first image reading unit and the image data read by the second image reading unit before the image processing unit performs the image processing. Thus, this image forming apparatus eliminates the image quality difference between the image data obtained separately by the two image reading units.
However, although the processing to correct the difference between the reading characteristics of the first image reading unit and the second image reading unit can be performed at a stage of the image processing by the correction processing unit where the output destination is not determined, the processing to correct the difference between the reading characteristics of the first image reading unit and the second image reading unit can not be performed at a stage of the image processing by the image processing unit where the correction is performed based on the writing characteristic of a writing unit that prints image data on a paper sheet after the output destination is determined to be the writing unit. Therefore, particularly when image data is printed on a paper sheet, it is difficult to make equal image quality to the printed images of the image data that have been read by reading units with different reading characteristics. When the image data that are acquired by reading units with different reading characteristics are printed on a single paper sheet by using a consolidating function, an image quality difference between the printed images of the image data shows up markedly.